A common type of window includes a rectangular frame set into a building wall and a corresponding vent connected to the frame by a hinge assembly. The hinge assembly can be oriented so that the vent can pivot about either a horizontal or a vertical axis. Thus, the vent can be opened by pivoting inward and downward about a horizontal axis. Various means are available for securing the vent at a selectable angle to make the opening larger or smaller. It is often desirable to limit the size of the opening; for example, the window might be located in a school, where it is clearly preferable that the opening not be large enough to permit unauthorized, unintended or accidental entry or exit. Prior hinge assemblies include limit mechanisms, to preclude the vent being opened wider than a desired limit.
However, it is also desirable that the vent occasionally be opened wider than the selected limit to permit the window to be cleaned or otherwise maintained from inside the building. Traditionally, the opening of the vent beyond the limited range required dismantling the hinge assembly in both the disassembly and reassembly of the hinge, which can involve an excessive amount of time and labor.
Therefore, a need exists to provide a mechanism, which normally limits the opening of the vent but also allows selective opening of the vent beyond a limited range. There is also a need to restrict the selective opening of the vent beyond the predetermined limit.